The answer for me (a set collector) is to buy a little of both.
There are still plenty of Lionel transformer sets on the market--many at great prices. As I add sets, it will first be these, since Lionel won't be making them anymore.
But that doesn't mean I don't like Lionchief. Lionchief sets are a good product. I have four and enjoy using them--they're fun! They fit in well with my conventional transformers, and while I can't run them and conventional trains on the same track at the same time, that doesn't matter to me. I run in independent loops so I can dedicate loops to conventional and loops to Lionchief. Will they hold up? Perhaps not as well as my 60 year old trains. But I've had to have those repaired, too. So, everything is relative.
And then there's MTH. As others have said, if you like transformer capability it's really very simple--MTH starter sets. What a great product.
Finally, as to affordability: I just bought the Lionchief Peanuts Halloween set off Amazon for $129--shipped. An amazing play value in that set. Mario on his website is offering a few MTH sets at under $300. I don't think one can argue that the hobby has no room at the bottom--if there wasn't any room, I wouldn't be in it! I don't buy $500+ engines (nothing wrong with that, but it's not for me), I buy <$400 starter sets, and many I get way under that price. For someone starting out, or train collectors like me, there are many, many affordable options.